'Loo' and 'Concentration Camp'; the innocent and sinister use of euphemism

Eupehemism runs very deep in our language it soften our linguistic palate for inedible words.

I am going to the 'loo' = euphemism for the thing in polite society that dare not speak its name.
And indeed innocent enough.

But the use of some euphemism are unforgivable: Concentration camp is itself a notorious euphemism for places whose whole purpose was extermination.